Refractory mortar composition



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REFRACTORY MORTAR COMPOSITION Original Filed Nov. 20, 1963 0566? MMCKE/V WM M lffdR/VIY United States Patent Ori al a plication Nov. 20

disarm and this applicatioh Oct. 14, 1965, Ser. No.

2 Claims- (Cl- 106-40) This application is a divisional application ofapplication Serial No. 325,019, filed November 20, 1963, and having thesame inventor, title and assignee as the present invention.

This invention relates to the construction of rotary kiln linings and,more particularly, to construction of basic refractory rotary kilnlinings in such as cement kilns or the like. In a specific aspect, theinvention relates to an improved method of constructing a basicrefractory lining in a rotary kiln of the type in which reducingconditions may exist. By reducing conditions, I mean the kilnatmosphere, during operation, is not oxidizing. Such conditions areencountered in certain rotary kiln operations in which an excess of fuelis introduced to the kiln over that which can stoichiometrically combinewith the available oxygen in the kiln. Some rotary kilns are operatedunder these conditions in order to increase output.

Contrary to what one might at first think, even though all of the fuelis not utilized, the operation is more economical because of theincreased output.

It has long been known in the art to provide metal cases about at leasta few of the side surfaces of the refractory brick or blocks which areused to fabricate rotary kiln linings. In theory and in operation, themetal plates oxidize and near the hot face react with the brick firmlybonding adjacent brick. The result is a monolithic lining more able toresist stresses and strains normally encountered in the operation of arotary kiln. When kilns are operated under reducing conditions, themetal plates do not oxidize and, under severely reducing conditions, maymelt and be partially absorbed by the refractory, the end result beingthe lack of bond and/ or monolithic structure besides having a generalloosening of the brickwork.

It is, therefore, an object of this invention to provide a novel methodof fabricating a basic refractory lining in a rotary kiln or the likewithout the use of metal plates. It is still another object of thisinvention to provide a novel method of fabricating basic refractory,rotary kiln lining capable of attaining monolithic characteristics underreducing operating conditions.

Briefly, according to one aspect of this invention, those portions of arotary kiln refractory lining which are subjected to reducing conditionsin operation, are installed without the use of metal plates. Rather, thebasic refractory brick or blocks used in this area are initiallyinstalled and temporarily joined together with a plastic and adhesivecomposition consisting essentially of at least about 50% finely dividediron oxide 0, about 40% of ball mill fine dead burned magnesite, andabout of a water-soluble hydrated powder sodium silicate (allpercentages, by weight). To install the brick, the adhesive compositionis mixed with about 25 to 30 parts, by weight, of water; and theresulting plastic mixture is trowelled or otherwise applied to the foursides of the brick or block, which are to be perpendicular or normal tothe longitudinal axis of the kiln. The prepared brick are then laid upabout the interior surface of the kiln shell in the normal manner. Theplastic mixture is air setting, and develops sufficient strength withina few hours to hold the brick in place about the kiln shell. The kiln isthen fired in the 3,285,762 Patented Nov. 15, 1966 normal manner, inwhich the above discussed reducing conditions are developed. The plasticcomposition undergoes chemical or mineralogical reaction to formmagnesio-ferrite within itself and by reaction with adjacent surfaceareas of the basic brick with which they are used.

In actual tests, brick made of refractory material of the type disclosedin Pitt et al., United States Patents 2,291,917 and 2,291,918, which arecommercially available as the manufacture of Canadian RefractoriesLimited, a Canadian corporation, under the trademark Magnecon, were laidup in a rotary kiln with a plastic composition according to thisinvention, which consisted essentially of:

Percent (by weight) Iron oxide (Fe o l00 mesh 50 Dead burned magnesite,-65 mesh 40 Sodium silicate, -l00 mesh 10 and up to about 1%, based onthe weight of solids of an organic plasticizer such as cornstarch, gumarabic, etc.

About 50% of this material being held on a 325 mesh screen. (Such amaterial is normally referred to as ball mill tines in the art.)

Hydrated powder sodium silicate, having 11 No.20 to S10: weight ratio of1: 3.22. The foregoing dry constituents were mixed with between 25 and30 parts, by weight, of water. The magnesite used was a synthetic deadburned magnesite, recovered from sea water, and having the followingapproximate oxide analysis, by weight:

The kiln was fired according to usual operating techniques, and verysatisfactory service was obtained. The plastic material had sufficientstrength to hold the brick in place until normal kiln operatingtemperatures were reached; and, at these operating temperatures,chemically or mineralogically reacted and bonded to the adjacent brickto provide a monolithic lining.

It should be understood that other types of dead burned magnesite,besides that given immediately above, can be used according to theconcepts of this invention. In fact, any of the many dead burnedmagnesites commercially available as items of commerce are usable. Theiron oxide is, preferably, technical grade, which is what was used inthe tests just discussed; and which is in the order of about pluspercent, Fe o The sodium silicate used should be in powder form andrelatively stable in storage. We know of other hydrated powder sodiumsilicates which can be used having sodium oxide to silicon dioxideweight ratios of 1:2.00 and 1:1. Either of these latter sodium silicatepowders are at least 65 mesh. I do not believe the particular sodiumsilicate used to be particularly critical, other than its ability toprovide suificient strength upon air setting to hold the brick in placebefore firing of the rotary kiln.

In laboratory tests, using various proportions of iron oxide and deadburned magnesite, it was discovered the iron oxide content may varybetween about 30 and about 50%. When the iron oxide content wasincreased to the order of 70% (all percentages herein referred to are byweight), very poor strength was developed after drying. For example, aMagnecon type brick was sawed in half, and then joined together with amixture having the following composition: 70% iron oxide, 20% deadburned magnesite, 10% hydrated powdered sodium silicate having an Na Oto $0, weight ratio of 1:3.2, about 0.2%, based on the weight of drysolids of cornstarch, and about 30 parts, by weight, based on the totalweight of dry solids of water, to bring the mixture to trowellingconsistency. After drying for about 12 hours at a temperature of about250 F., the adhesive joint had a modulus of rupture of only 170 p.s.i.After heating to 1700 F., the joint powdered and had no measurablestrength in a modulus of rupture test.

In a comparative test using the preferred composition of the inventionas set forth above (50% iron oxide, 40% of the magnesite and 10% sodiumsilicate powder) the modulus of rupture after drying under identicalconditions was 400 p.s.i. After heating to 1700 F., modulus of rupturewas about 70 p.s.i.

It was, also, found that up to about 10 parts, by weight, of a veryfinely divided (325 mesh) ball clay plasticizer (such as air floatedball clay) could be substituted for a portion of the dead burnedmagnesite, as one approached the lower operable composition limit ofabout 30 parts, by weight, iron oxide.

Therefore, satisfactory compositions have from about 30 to about 50%finely divided (at least 65 mesh) iron oxide, 20 to about 50%, byweight, ball mill fine dead burned magnesite, 0 to about 10%, by weight,of finely divided ball clay plasticizer, and about 10%, by weight, ofsodium silicate having a sodium oxide to silicon dioxide weight ratio inthe range 1:1 to 1:3.22. The sodium silicate addition can vary in therange about to about 15%, by weight, of the total solids. As the percentof sodium silicate varies, there should be a corresponding increase ordecrease in the ball mill fine dead burned magnesite, for example.

The tempering fluid (preferably water) used to bring the mixture totrowelling consistency is, of course, variable, and depends upon thebrick mason and his idiosyncrasies as to workability, but I suggestbetween about 25 and 30 parts, by weight.

Superior results are obtained when the iron oxide addition is maintainedbetween about 45 and 55%, by weight, of the total solids. Optimumresults were obtained when the iron oxide amounts to about 50%, byweight, as set forth in the embodiment as discussed above, relative toactual trials in a rotary cement kiln.

Still further, tests were conducted in the laboratory by heating a testbrick (a Magnecon type brick sawed in half and then rejoined with theplastic composition of the invention) to about 2600 F. under reducingconditions. The preferred composition was visually determined to havevery fine cracks. The workable, but less satisfactory, compositions,having only about 30% of iron oxide, had slightly larger cracks. Acomposition having 70% of the iron oxide (the one discussed above) wasvisually determined to have cracks as large as Me".

In discussing the sizing of the various dry ingredients, above, it wasmentioned that the magnesite was ball mill fines or nominally 65 mesh.Satisfactory results can be obtained using magnesite which includessomewhat larger particles; for example, of the mix can be about 28 +65mesh dead burned magnesite. Further, trace amounts, i.e. up to about 2or 3%, by weight, of the total batch, can be about 28 +65 mesh deadburned magnesite. Further, trace amounts, i.e. up to about 2 or 3%, byweight, of the total batch, can be 10 +28 mesh.

I am aware that prior workers in the art have suggested use of iron ormetal filings, metal shot and the like, perhaps in combination with someiron oxide, as hardened coatings for hydratable brick. I am, also, awarethat iron oxide has been suggested, in combination with otheringredients such as aluminum or magnesium metal, to form a thermite-typeproduct which can be used as a mortar; and which is ignited to producean exothermic reaction. Iron-base alloys such as ferro-chrome andferro-titanium have also been apparently suggested to coat brick.

The drawings are schematically indicative of a manner in which themethod of this invention can be carried out in laying up a rotary kilnlining. FIG. 1 is a schematic and view of a rotary kiln; and FIG. 2 isan enlarged perspective view of a portion of the kiln of FIG. 1,indicating the manner in which a rotary kiln lining is laid up accordingto this invention.

The exterior cylindrical rotary kiln shell 10 has a plurality of basicrefractory brick 11 circumferentially positioned about its interiorsurface. The brick are held initially or temporarily in place by theadhesive composition 12, according to this invention. As isconventional, a wooden framework 9 is used to hold the brick 11 inplace, while the adhesive of joints 12 is allowed to set. Upon firing, achemical or mineralogical reaction occurs through the adhesive 12 andwith the adjacent brick 11 to form a monolithic lining internally of theshell 10. The adhesive 12 is applied only to the surfaces or sides ofthe brick 11, which are normal to the longitudinal axis of the kilnshell 10. It is undesirable to use the adhesive on that face adjacentthe kiln shell, as this might cause joinder of the brick to the shell10. Such a condition would consider ably increase the difiiculties ofsubsequent removal of the lining when replacement is necessary. Further,it is not desirable to place any of the adhesive on the interfaces 11Aof the brick, as this would probably contaminate the kiln product, andwould really serve no use in the installation.

Having thus described the invention in detail and with sufficientparticularity as to enable those skilled in the art to practice it, whatis desired to have protected by Letters Patent is set forth in thefollowing claims.

I claim:

1. An adhesive composition for laying up basic refractory brickconsisting essentially of a mixture of from 45 to about 50%, by weight,of 65 mesh iron oxide, 20 to 50%, by weight, of ball mill fine deadburned magnesite, 0 to 10%, by weight, of finely divided ball clayplasticizer, about 5 to 15%, by weight, of powder sodium silicate havinga sodium oxide to silicon dioxide weight ratio between 1:1 to 1:3.2, andan effective amount of an organic plasticizer to provide plasticity.

2. An adhesive composition for laying up basic refractory brickconsisting essentially of a mixture of from 30 to about 55%, by weight,of 65 mesh iron oxide, 20 to 45%, by weight, of ball mill fine deadburned magnesite, 0 to 10%, by weight, of finely divided ball clayplasticizer, about 5 to 15%, by weight, of powder sodium silicate havinga sodium oxide to silicon dioxide weight ratio between 1:1 to 1:322, andan effective amount of an organic plasticizer to provide plasticity.

References Cited by the Examiner UNITED STATES PATENTS 2,170,254 8/1939Seil 264-

1. AN ADHESIVE COMPOSITION FOR LAYING UP BASIC REFRACTORY BRICKCONSISTING ESSENTIALLY OF A MIXTURE OF FROM 45 TO ABOUT 50%, BY WEIGHT,OF -65 MESH IRON OXIDE, 20 TO 50%, BY WEIGHT, OF BALL MILL FINE DEADBURNED MAGNESITE, 0 TO 10%, BY WEIGHT, OF FINELY DIVIDED BALL CLAYPLASTICIZER, ABOUT 5 TO 15%, BY WEIGHT, OF POWDER SODIUM SILICATE HAVINGA SODIUM OXIDE TO SILICON DIOXIDE WEIGHT RATIO BETWEEN 1:1 TO 1:3.2, ANDAN EFFECTIV AMOUNT OF AN ORGANIC PLASTICIZER TO PROVIDE PLASTICITY.